Hitachi WH 12DM2 Mode D'emploi page 16

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(5) Using optional parts (WR12DM2, WR9DM2)
The tightening torque is reduced a little when an
extension bar, universal joint or a long socket is
used.
(6) Clearance of the socket (WR12DM2, WR9DM2)
A worn or deformed hex. or a square-holed socket
will not give an adequate tightness to the fitting
between the nut or anvil, consequently resulting in
loss of tightening torque.
Using an improper socket which does not match to
the bolt will result in an insufficient tightening torque.
Matching socket and bolt sizes are shown in Table 1,
2, 3 and 4.
For WH12DM2
kgf·cm N·m
M10 × 30
1000 100
High tension bolt
800 80
600 60
400
40
Ordinary bolt
200 20
0 0
0 1
Tightening time: sec.
(Steel plate thickness
t = 10 mm)
For WH9DM2
N·m M8 × 30
kgf·cm
100
1000
80
800
High tension bolt
60
600
40
400
20
200
0 0
0 1
Tightening time: sec.
(Steel plate thickness
t = 10 mm)
15
kgf·cm
1400
1200
1000
800
600
400
200
0
2 3
kgf·cm
1000
800
600
400
200
0
2 3
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
(7) Tightening torque varies, depending on the battery's
charge level. (WR12DM2, WR9DM2)
Fig. 28 and 29 show examples of the relationship
between tightening torque and the number of
tightenings, for WR12DM2 and WR9DM2. As shown,
tightening torque gradually weakens with the increase
in the number of tightenings. In particular, as the
torque decreases very close to the complete discharge
("a" margin in graph), the unit's impact weakens, the
number of time impacts declines and tightening
torque drops off abruptly. If this occurs, check torque
level, then recharge the battery if necessary.
N·m
M12 × 45
140
120
100
High tension bolt
80
60
Ordinary bolt
40
20
0
0 1 2 3
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
Fig. 22
N·m M10 × 30
100
High tension bolt
80
60
40
Ordinary bolt
20
0
0 1 2 3
Fig. 23
kgf·cm N·m
M14 × 50
1400 140
1200
120
High tension bolt
1000 100
800 80
600 60 Ordinary bolt
400
40
200 20
0 0
0 1
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
M12 × 45
kgf·cm N·m
120
1200
100
1000
High tension bolt
80
800
60
600
40 Ordinary bolt
400
200 20
0 0
0 1 2
Tightening time: sec.
(Steel plate thickness
t = 25 mm)
2 3
3